A super junction structure adopts an alternating P type and N type structure to replace the N drift region of a traditional VDMOS (Vertical Double-Diffused Metal Oxide Semiconductor). By using the well-known VDMOS manufacturing process, the super junction structure can be applied to the fabrication of a MOSFET so as to manufacture a super junction MOSFET. Since a super junction MOSFET adopts a low resistance epitaxial layer, a much lower on resistance can be achieved while maintaining a same breakdown voltage as a traditional VDMOS.
Generally, there are two ways to form an alternating P type and N type structure, namely by multiple epitaxial growths or by deep trench filling, wherein the method of deep trench filling has become a trend in development of super junction high voltage process due to its advantages of low cost and short process time. During the process of manufacturing a super junction device, the step of forming deep trenches is of vital importance as the depth and profile of the deep trench will influence the performance of the super junction device manufactured. Preferably, the deep trench should have a depth equal or nearly equal with the thickness of the epitaxial layer in which the deep trench is formed; besides, the profile of the deep trench should be vertical so as to make sure that the silicon filled in the deep trench has a good uniformity of concentration. After deep trench filling, CMP process is used to planarize the surface of the deep trenches, so that an alternating P type and N type structure is finished. The problem is that the process of deep trench etching and tilling is very difficult to control, and the manufacturing cost is very high.